Propagation Effects

Effect	Description	Worst at
Rain attenuation	Absorption/scattering by rain	Ku, Ka+
Atmospheric absorption	Oxygen and water vapour	Microwave/mmWave
Scintillation	Rapid fluctuation from the atmosphere/ionosphere	Low elevation
Faraday rotation	Polarization rotation by the ionosphere	Lower bands
Doppler shift	Frequency shift from relative motion	LEO/MEO
Sun outage	Solar noise behind the satellite	GEO near equinox

Satellite propagation effects.

Caution

Key Formula — Rain specific attenuation

$$\gamma_R=kR^{\alpha}\ (dB/km),$$

$R$ = rain rate (mm/h); $k,\alpha$ depend on frequency and polarization.

Above 10 GHz, rain attenuation is the dominant weather loss. Mitigate it with a larger link margin, uplink power control, a larger antenna, a lower band where possible, adaptive coding/modulation and site diversity.